EP3958001B1 - Opto-mechanical resonator with two or more frequency modes - Google Patents
Opto-mechanical resonator with two or more frequency modes Download PDFInfo
- Publication number
- EP3958001B1 EP3958001B1 EP21189745.9A EP21189745A EP3958001B1 EP 3958001 B1 EP3958001 B1 EP 3958001B1 EP 21189745 A EP21189745 A EP 21189745A EP 3958001 B1 EP3958001 B1 EP 3958001B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- optical signal
- resonator
- resonance frequency
- modulated
- reflected
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 230000003287 optical effect Effects 0.000 claims description 296
- 230000001133 acceleration Effects 0.000 claims description 89
- 238000012545 processing Methods 0.000 claims description 55
- 238000000034 method Methods 0.000 claims description 31
- 230000007423 decrease Effects 0.000 claims description 20
- 230000010355 oscillation Effects 0.000 claims description 11
- 230000008859 change Effects 0.000 description 13
- 230000006835 compression Effects 0.000 description 13
- 238000007906 compression Methods 0.000 description 13
- 230000015654 memory Effects 0.000 description 12
- 230000006870 function Effects 0.000 description 11
- 238000010586 diagram Methods 0.000 description 8
- 238000006073 displacement reaction Methods 0.000 description 8
- 230000000875 corresponding effect Effects 0.000 description 7
- 230000004044 response Effects 0.000 description 7
- 230000009286 beneficial effect Effects 0.000 description 5
- 230000007613 environmental effect Effects 0.000 description 5
- 238000009826 distribution Methods 0.000 description 4
- 230000005684 electric field Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- 238000004891 communication Methods 0.000 description 3
- 230000002596 correlated effect Effects 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 238000013500 data storage Methods 0.000 description 2
- 239000003989 dielectric material Substances 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000001459 lithography Methods 0.000 description 2
- 230000010363 phase shift Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 229910002601 GaN Inorganic materials 0.000 description 1
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 description 1
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- KXNLCSXBJCPWGL-UHFFFAOYSA-N [Ga].[As].[In] Chemical compound [Ga].[As].[In] KXNLCSXBJCPWGL-UHFFFAOYSA-N 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 230000001010 compromised effect Effects 0.000 description 1
- 238000004590 computer program Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000007274 generation of a signal involved in cell-cell signaling Effects 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- XCAUINMIESBTBL-UHFFFAOYSA-N lead(ii) sulfide Chemical compound [Pb]=S XCAUINMIESBTBL-UHFFFAOYSA-N 0.000 description 1
- 238000012886 linear function Methods 0.000 description 1
- 230000007787 long-term memory Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 238000012887 quadratic function Methods 0.000 description 1
- 230000006403 short-term memory Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/03—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses by using non-electrical means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/093—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by photoelectric pick-up
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H13/00—Measuring resonant frequency
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/097—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by vibratory elements
Definitions
- This disclosure relates to accelerometers.
- Accelerometers function by detecting a displacement of a proof mass under inertial forces.
- an accelerometer may detect the displacement of a proof mass by the change in frequency of a resonator connected between the proof mass and a support base.
- a resonator may be designed to change frequency proportional to the load applied to the resonator by the proof mass under acceleration.
- the resonator may be electrically coupled to oscillator circuitry, or other signal generation circuitry, which causes the resonator to vibrate at a resonance frequency.
- EP3112879A1 discloses systems, devices, techniques, and methods for an opto-mechanical vibrating beam accelerometer.
- a system is configured to couple a laser into optical resonance with opto-mechanically active (OMA) anchors suspending a proof mass.
- OMA opto-mechanically active
- the system measures an acceleration based on instantaneous resonance frequencies of the OMA anchors through changes to the amplitude or phase of the modulated laser.
- US10705112B1 discloses an optomechanical device comprising a circuit configured to generate an optical signal using a tuning signal and modulate the optical signal at a frequency corresponding to one quarter of a Full Width at Half Maximum (FWHM) of an optical resonance of the proof mass assembly to generate a partially modulated optical signal.
- FWHM Full Width at Half Maximum
- This disclosure is directed to devices, systems and techniques for determining an acceleration of a vibrating beam accelerometer (VBA).
- VBA vibrating beam accelerometer
- the disclosure is directed to a VBA with a proof mass, a base section, and a resonator beam.
- the resonator beam may be configured to receive a first optical signal and a second optical signal, which induce the resonator to vibrate at a first resonance frequency and a second resonance frequency, respectively.
- the respective magnitudes of resonance frequencies of the resonator beam may indicate the acceleration of the VBA. That is, the first resonance frequency and the second resonance frequency may change based on the acceleration of the VBA and it may be possible to determine the acceleration of the VBA based on the first resonance frequency and the second resonance frequency.
- a first negative feedback loop may control a first light-emitting device to emit the first optical signal at the first resonance frequency and a second negative feedback loop control a second light-emitting device to emit the second optical signal at the second resonance frequency.
- the resonator may pass a first portion of the first optical signal and reflect a second portion of the first optical signal.
- the resonator may pass a first portion of the second optical signal and reflect a second portion of the second optical signal.
- the first portion of the first optical signal may represent a portion of the first optical signal representing the first resonance frequency and the first portion of the second optical signal may represent the portion of the second resonance frequency representing the second resonance frequency.
- the reflected portions of the first optical signal and the second optical signals may represent portions that do not represent the first resonance frequency and the second resonance frequency, respectively.
- the processing circuitry may generate a first error signal to adjust the first optical signal emitted by the first light-emitting device in order to eliminate frequencies other than the first resonance frequency and the processing circuitry may generate a second error signal to adjust the second optical signal emitted by the second light-emitting device in order to eliminate frequencies outside of the second resonance frequency
- a photoreceiver may receive the first portion of the first optical signal, the second portion of the first optical signal, the first portion of the second optical signal, and the second portion of the second optical signal.
- the photoreceiver may generate one or more electrical signals which represent the optical signals received by the photoreceiver and output the one or more electrical signals to the processing circuitry.
- the processing circuitry may generate the first error signal based on the first portion of the first optical signal and generate the second error signal based on a first portion of the second optical signal.
- the processing circuitry may output the first error signal to the first light-emitting device in order to regulate the first optical signal to represent the first resonance frequency and the processing circuitry may output the second error signal to the second light-emitting device in order to regulate the second optical signal to represent the second resonance frequency.
- the processing may determine the acceleration of the VBA based on the first resonance frequency indicated by the first portion of the first optical signal and the second resonance frequency indicated by the first portion of the second optical signal. For example, a relationship may exist between a difference between a magnitude of the first resonance frequency of the resonator and a magnitude of the second resonance frequency of the resonator and the acceleration of the VBA. As such, the processing circuitry may calculate the acceleration of the VBA based on a difference between the first and second resonance frequencies of the resonator.
- readout signals of some accelerometers may be compromised by environmental factors such as temperature. It may be the case that a sole resonance frequency component of a resonator is affected by a temperature of an environment proximate to the VBA, thus affecting an acceleration which is measured based on one resonance frequency of one light mode.
- One or more techniques of this disclosure include determining an acceleration of a VBA based on a difference between two or more resonance frequencies, each resonance frequency of the two or more resonance frequencies corresponding to a different light mode.
- Environmental factors may affect each resonance frequency of the two or more resonance frequencies by substantially the same amount, thus eliminating an impact of the environmental factors on the measured acceleration.
- a change in temperature may cause both of the first resonance frequency and the second resonance frequency to change by the same amount while acceleration remains constant.
- the difference between the first resonance frequency and the second resonance frequency remains the same, which means that the measured acceleration remains the same.
- FIG. 1 is a block diagram illustrating an accelerometer system 10, in accordance with one or more techniques of this disclosure.
- accelerometer system 10 includes processing circuitry 12, resonator beam 20, proof mass 22, first light-emitting device 24, first modulator 25, first circulator 26, photoreceiver 28, second light-emitting device 32, second modulator, and second circulator 34.
- Accelerometer system 10 is configured to determine an acceleration based on two or more measured resonance frequencies of resonator beam 20, which is mechanically connected to proof mass 22.
- proof mass 22 may be capable of applying one or both of a compression force and a tension force to resonator beam 20, affecting the two or more resonance frequencies used to determine the acceleration.
- a first resonance frequency and a second resonance frequency may each change based on the change a magnitude of the force applied to resonator beam 20 by proof mass 22, where the change in the magnitude of the force is correlated with a change in the acceleration of accelerometer system 10.
- accelerometer system 10 may calculate the acceleration based on the difference between the first resonance frequency mode and the second resonance frequency mode.
- Processing circuitry 12 may include one or more processors that are configured to implement functionality and/or process instructions for execution within accelerometer system 10.
- processing circuitry 12 may be capable of processing instructions stored in a memory.
- Processing circuitry 12 may include, for example, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or equivalent discrete or integrated logic circuitry, or a combination of any of the foregoing devices or circuitry. Accordingly, processing circuitry 12 may include any suitable structure, whether in hardware, software, firmware, or any combination thereof, to perform the functions ascribed herein to processing circuitry 12.
- a memory may be configured to store information within accelerometer system 10 during operation.
- the memory may include a computer-readable storage medium or computer-readable storage device.
- the memory includes one or more of a short-term memory or a long-term memory.
- the memory may include, for example, random access memories (RAM), dynamic random access memories (DRAM), static random access memories (SRAM), magnetic discs, optical discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable memories (EEPROM).
- the memory is used to store program instructions for execution by processing circuitry 12.
- Resonator beam 20 may represent a mechanical beam which is located between proof mass 22 and a base section (not illustrated in FIG. 1 ).
- Proof mass 22 in some cases, may apply a tension force to resonator beam 20 or apply a compression force to resonator beam 20.
- resonator beam may be configured to mechanically vibrate according to two or more resonance frequencies, When proof mass 22 applies a tension force to resonator beam 20 in response to an acceleration in a first direction 58, the tension force may "pull" on first end 52 and second end 54 of resonator beam 20 and a magnitude of each resonance frequency of the one or more resonance frequencies may change by a predetermined amount corresponding to a magnitude of the tension force.
- the compression force may "push" on first end 52 and second end 54 of resonator beam 20 and the magnitude of each resonance frequency of the two or more resonance frequencies may change by a predetermined amount corresponding to a magnitude of the compression force.
- tension forces and compression forces applied to resonator beam 20 responsive to acceleration in the first direction 58 and the second direction 60, respectively, may affect characteristics (e.g., magnitude) of the two or more resonance frequencies by which resonator beam 20 vibrates. Measuring the magnitude and the sign (e.g., positive or negative) of each resonance frequency of the two or more resonance frequencies may allow processing circuitry 12 to determine a magnitude and a sign of the acceleration of accelerometer system 10. For example, processing circuitry 12 may determine the acceleration based on one or more electrical signals generated by photoreceiver 28, which indicate the difference between a first resonance frequency of resonator 20 and a second resonance frequency of resonator 20.
- First light-emitting device 24 and second light-emitting device 32 may, in some cases, include one or more laser devices configured to emit photons.
- light-emitting devices 24, 32 emit photons at an optical power within a range between 0.1 microwatts ( ⁇ W) and 10 ⁇ W.
- first light-emitting device 24 is a first semiconductor laser which includes a first laser diode and second light-emitting device 32 is a second semiconductor laser which includes a second laser diode.
- First light-emitting device 24 may generate a first optical signal 44' based on a first error signal received from processing circuitry 12.
- Second light-emitting device 32 may generate a second optical signal 48' based on a second error signal received from processing circuitry 12.
- First modulator 25 and second modulator 33 may modulate optical signals emitted by the first light-emitting device 24 and the second light-emitting device 32, respectively.
- First modulator 25, for example, may receive first optical signal 44' from first light-emitting device 24 while first modulator 25 also receives a first modulator control signal from a first control unit (not illustrated in FIG. 1 ) which regulates a manner in which first modulator 25 modulates the first optical signal.
- First modulator 25, in some cases, may transmit a modulated first optical signal 44 to first circulator 26.
- second modulator 33 may receive second optical signal 48' from second light-emitting device 32 while second modulator 33 also receives a second modulator control signal from a second control unit (not illustrated in FIG. 1 ) which regulates a manner in which second modulator 33 modulates the second optical signal. Second modulator 33, in some cases, may transmit a modulated second optical signal 48 to second circulator 34.
- First circulator 26 and second circulator 34 may represent optical devices configured to receive optical signals via one or more optical inputs and output optical signals via one or more optical outputs.
- first circulator 26 includes first optical inputs 36A-36C (collectively, “first optical inputs 36") and first circulator 26 also includes first optical outputs 38A-38C (collectively, “first optical outputs 38").
- Second circulator 34 includes second optical inputs 40A-40C (collectively, “second optical inputs 40") and second circulator 34 also includes second optical outputs 42A-42C (collectively, “optical outputs 42").
- First light-emitting device 24 generates a first optical signal 44' and outputs the first optical signal 44' to first modulator 25.
- First modulator 25 modulates the first optical signal 44' in order to generate a modulated first optical signal 44.
- first modulator 25 receives a first modulator control signal which causes first modulator 25 to generate modulated first optical signal 44 according to a first light mode.
- First modulator 25 outputs the modulated first optical signal 44 to first circulator 26 via optical input 36A.
- First circulator 26 may direct modulated first optical signal 44 to a first end 52 of resonator beam 20 via optical output 38A.
- the modulated first optical signal 44 may travel through resonator beam 20 to a position proximate a center 56 of resonator beam 20.
- modulated first optical signal 44 may include a range of optical frequencies.
- Resonator beam 20 may reflect some optical frequencies of modulated first optical signal 44 and allow some optical frequencies of modulated first optical signal 44 to pass through the length of resonator beam 20 from first end 52 to second end 54.
- Resonator beam 20 may reflect a first portion of modulated first optical signal 44 and allow a second portion of modulated first optical signal 44 to pass through resonator beam 20 from the first end 52 to the second end 54.
- the second portion of modulated first optical signal 44 which exits the second end 54 of resonator beam 20 may represent a "passed" first optical signal 45.
- Resonator beam 20 may reverse a direction of the first portion of the modulated first optical signal 44 which is reflected, causing the first portion of the modulated first optical signal 44 to exit at the first end 52 of resonator beam 20.
- the optical signal exiting the first end 52 of resonator beam 20 may represent a "reflected" first optical signal 46.
- the first portion of modulated first optical signal 44 includes one or more bands of frequencies and the second portion of modulated first optical signal 44 represents a narrow band of frequencies which indicate a first resonance frequency of resonator beam 20.
- the first lighting mode of the modulated first optical signal 44 may, in some cases, represent a Transverse Electric (TE) lighting mode. Light which propagates according to the TE lighting mode may be referred to herein as "TE Light.” TE light represents light which does not induce an electric field in a direction of propagation and does induce a magnetic field in the direction of propagation. For example, as modulated first optical signal 44 propagates from the first end 52 of resonator beam 20 towards the center 56 of resonator beam 20, modulated first optical signal 44 induces a magnetic field in a horizontal direction (e.g., the direction along resonator beam 20 from the first end 52 to the second end 54) relative to resonator beam 20 and does not induce an electric field in the horizontal direction.
- a horizontal direction e.g., the direction along resonator beam 20 from the first end 52 to the second end 54
- the TE light of modulated first optical signal 44 may cause resonator beam 20 to vibrate mechanically at a first resonance frequency which corresponds to the TE lighting mode.
- the passed first optical signal 45 may, in turn, indicate the first resonance frequency of resonator beam 20.
- First circulator 26 may receive the reflected first optical signal 46 via optical input 36B. Then, first circulator 26 outputs the reflected first optical signal 46 to photoreceiver 48 via optical output 38B.
- Second light-emitting device 32 generates a second optical signal 48' and outputs the second optical signal 48' to second modulator 33.
- Second modulator 33 modulates the second optical signal 48' in order to generate a modulated second optical signal 48.
- second modulator 33 receives a second modulator control signal which causes second modulator 33 to generate modulated second optical signal 48 according to a second light mode.
- Second modulator 33 outputs the modulated second optical signal 48 to second circulator 34 via optical input 40A.
- Second circulator 34 may direct modulated second optical signal 48 to the second end 54 of resonator beam 20 via optical output 42A.
- the modulated second optical signal 48 may travel through resonator beam 20 to a position proximate a center 56 of resonator beam 20.
- modulated second optical signal 48 may include a range of optical frequencies.
- Resonator beam 20 may reflect some optical frequencies of modulated second optical signal 48 and allow some optical frequencies of modulated second optical signal 48 to pass through the length of resonator beam 20 from second end 54 to first end 52.
- Resonator beam 20 may reflect a first portion of modulated second optical signal 48 and allow a second portion of modulated second optical signal 48 to pass through resonator beam 20 from the second end 54 to the first end 52.
- the second portion of modulated second optical signal 48 which exits the first end 52 of resonator beam 20 may represent a "passed" second optical signal 49.
- Resonator beam 20 may reverse a direction of the first portion of the modulated second optical signal 48 which is reflected, causing the first portion of the modulated second optical signal 48 to exit at the second end 54 of resonator beam 20.
- the optical signal exiting the second end 54 of resonator beam 20 may represent a "reflected" second optical signal 50.
- the first portion of modulated second optical signal 48 includes one or more bands of frequencies and the second portion of modulated second optical signal 48 represents a narrow band of frequencies which indicate a second resonance frequency of resonator beam 20.
- the second lighting mode of the modulated second optical signal 48 may, in some cases, represent a Transverse Magnetic (TM) lighting mode. Light which propagates according to the TM lighting mode may be referred to herein as "TM Light.” TM light represents light which does not induce a magnetic field in a direction of propagation and does induce an electric field in the direction of propagation. For example, as modulated second optical signal 48 propagates from the second end 54 of resonator beam 20 towards the center 56 of resonator beam 20, modulated second optical signal 48 induces an electrical field in a horizontal direction (e.g., the direction along resonator beam 20 from the second end 54 to the first end 52) relative to resonator beam 20 and does not induce a magnetic field in the horizontal direction.
- a horizontal direction e.g., the direction along resonator beam 20 from the second end 54 to the first end 52
- the TM light of modulated second optical signal 48 may cause resonator beam 20 to vibrate mechanically at a second resonance frequency which corresponds to the TM lighting mode.
- the passed second optical signal 49 may, in turn, indicate the second resonance frequency of resonator beam 20.
- Second circulator 34 may receive the reflected second optical signal 50 via optical input 40B. Then, second circulator 34 outputs the reflected second optical signal 50 to photoreceiver 48 via optical output 42B.
- First circulator 26 may receive passed second optical signal 49 via optical input 36C and forward passed second optical signal 49 to photoreceiver 28 via optical output 38C.
- Second circulator 33 may receive passed first optical signal 45 via optical input 40C and forward passed first optical signal 45 to photoreceiver 28 via optical output 42C.
- modulated first optical signal 44 is described herein as including TE light and modulated second optical signal 48 is described herein as including TM light, this is not required.
- modulated first optical signal 44 includes TM light and modulated second optical signal 48 may include TE light.
- first optical signal 44 and second optical signal 48 may include one or more other types of light which cause resonator beam 20 to mechanically vibrate according to two different modes.
- photoreceiver 28 may include one or more transistors configured to absorb photons of one or more optical signals and output, in response to absorbing the photons, an electrical signal. In this manner, photoreceiver 28 may be configured to convert optical signals into electrical signals.
- Photoreceiver 20 receives the passed first optical signal 45, the reflected first optical signal 46, the passed second optical signal 49, and the reflected second optical signal 50.
- Photoreceiver 28, for example, may include one or more p-n junctions that convert the photons of one or more optical signals into corresponding electrical signals.
- photoreceiver 28 may generate a first electrical signal component based on the passed first optical signal 45 and generate a second electrical signal component based on the passed second optical signal 49.
- the first electrical signal component may preserve at least some of the parameters of passed first optical signal 45 and the second electrical signal component may preserve at least some of the parameters of passed second optical signal 49.
- the first electrical signal component may indicate the first resonance frequency (e.g., the TE resonance frequency) which is indicated by the passed first optical signal 45.
- the second electrical signal component may indicate the second resonance frequency (e.g., the TM resonance frequency) which is indicated by the passed second optical signal 49.
- One or more frequency values and intensity values associated with passed first optical signal 45 and passed second optical signal 49 may be indicated by the first electrical signal component and the second electrical signal component, respectively.
- photoreceiver 28 may produce a stronger electrical signal (i.e., greater current magnitude) in response to receiving a stronger (e.g., greater power) optical signal.
- Photoreceiver 28 may include semiconductor materials such as any one or combination of Indium Gallium Arsenide, Silicon, Silicon Carbide, Silicon Nitride, Gallium Nitride, Germanium, or Lead Sulphide.
- a difference between the TE resonance frequency and the TM resonance frequency might, in some cases, be correlated with an acceleration of accelerometer system 10.
- a first difference between the TE resonance frequency and the TM resonance frequency may represent a first acceleration and a second difference between the TE resonance frequency
- the TM resonance frequency may represent a second acceleration.
- the first difference is greater than the second difference
- the first acceleration may be greater than the second acceleration.
- the first difference is less than the second difference
- the first acceleration may be less than the second acceleration.
- processing circuitry 12 may be configured to apply the relationship in order to calculate the acceleration of accelerometer system 10 based on the difference between the TE resonance frequency and the TM resonance frequency indicated by the electrical signal.
- the difference between TE resonance frequency and the TM resonance frequency is a difference between two frequency values and does not represent a single frequency magnitude value.
- environmental factors such as a temperature in an area proximate to the accelerometer system 10 may affect the TE resonance frequency and the TM resonance frequency by the same or similar factors, meaning that the difference between the TE resonance frequency and the TM resonance frequency is not substantially affected by these environmental factors, which is beneficial.
- the TE resonance frequency and the TM resonance frequency may be the same while the acceleration of accelerometer system 10 is zero. For example, it may be easier to determine a difference between a positive acceleration of accelerometer system 10 and a negative acceleration of accelerometer system 10 when a difference between the TE resonance frequency and the TM resonance frequency is not the same while the acceleration of accelerometer system 10 is zero.
- processing circuitry 12 is configured to generate a first error signal for output to first light-emitting device 24.
- processing circuitry 12 generates the first error signal in order to cause first light-emitting device 24 to generate first optical signal 44' to include one or more frequency components corresponding to the first resonance frequency of resonator 20.
- Resonator 20 may reflect any portions of the first modulated optical signal 44 which are outside of the narrow band of frequencies which represent the first resonance frequency. These reflected portions are represented by reflected first optical signal 46.
- Processing circuitry 12 may generate the first error signal based on one or more parameters of the reflected first optical signal 46 in order to cause an entirety of modulated first optical signal 44 to pass through resonator 20. In other words, when the error signal is equal to zero, a magnitude of reflected first optical signal 46 is zero and an entirety of modulated first optical signal 44 passes through resonator 20.
- processing circuitry 12 is configured to generate a second error signal for output to second light-emitting device 32.
- processing circuitry 12 generates the second error signal in order to cause second light-emitting device 32 to generate second optical signal 48' to include one or more frequency components corresponding to the second resonance frequency of resonator 20.
- Resonator 20 may reflect any portions of the second modulated optical signal 48 which are outside of the narrow band of frequencies which represent the second resonance frequency. These reflected portions are represented by reflected second optical signal 50.
- Processing circuitry 12 may generate the second error signal based on one or more parameters of the reflected second optical signal 50 in order to cause an entirety of modulated second optical signal 48 to pass through resonator 20. In other words, when the error signal is equal to zero, a magnitude of reflected second optical signal 50 is zero and an entirety of modulated second optical signal 48 passes through resonator 20.
- accelerometer system 10 may only allow the measurement of an acceleration along a single proof mass displacement axis, thus allowing accelerometer system 10 to measure acceleration along one Cartesian axis only.
- the proof mass displacement axis of accelerometer system 10 is parallel to first direction 58 and parallel to second direction 60. For example, when proof mass 22 is "displaced" closer to resonator beam 20 along the proof mass displacement axis, this may cause a tension force to be applied to resonator beam 20 which in turn causes resonance frequency modes to shift proportional to the acceleration of proof mass 22.
- three accelerometer systems are placed on the object such that the proof mass displacement axes of the respective accelerometer systems are aligned to form an x-axis, a y-axis, and a z-axis of a Cartesian space.
- readouts from each of the three accelerometer systems may be combined to determine a three-dimensional acceleration vector.
- Accelerometer system 10 is configured to measure the acceleration of the object in real-time or near real-time. Since processing circuitry 12 determines one or more resonance frequencies of resonator beam 20 based on optical signals which travel at the speed of light, processing circuitry 12 may be configured to determine the acceleration of accelerometer system 10 within a very short latency period (e.g., less than one nanosecond (ns)). In other words, processing circuitry 12 may determine the acceleration of accelerometer system 10 at a time that is very close to a present time, such as a time less than one nanosecond preceding the present time.
- a very short latency period e.g., less than one nanosecond (ns)
- accelerometer system 10 may be a part of an inertial navigation system (INS) for tracking a position of an object based, at least in part, on an acceleration of the object. Additionally, accelerometer system 10 may be located on or within the object such that accelerometer system 10 accelerates with the object. As such, when the object accelerates, accelerometer system 10 (including proof mass 22 and resonator beam 20) accelerates with the object.
- INS inertial navigation system
- processing circuitry 12 may, in some cases, be configured to determine the position displacement of the object by performing a double integral of the acceleration of the object over the period of time. Determining a position of an object using accelerometer system 10 located on the object, and not using a navigation system separate from the object (e.g., a Global Positioning System (GPS)), may be referred to as "dead reckoning.”
- GPS Global Positioning System
- FIG. 2 is a block diagram illustrating a proof mass assembly 14 and a circuit 16, in accordance with one or more techniques of this disclosure.
- proof mass assembly 14 includes proof mass 22, middle section 62, and base section 64.
- Resonator beam 20 may be located on, within, or otherwise in contact with middle section 62.
- Circuit 16 may represent an opto-electrical circuit configured to emit one or more optical signals to proof mass assembly 14.
- circuit 16 includes processing circuitry 12, first light-emitting device 24, first circulator 26, photoreceiver 28, second light-emitting device 32, and second circulator 34 of FIG. 1 .
- proof mass 22 is mechanically connected to middle section 62, and middle section 62 is mechanically connected to base section 64.
- Proof mass 22 may apply one or both of compression forces and tension forces to resonator beam 20 by nature of being mechanically connected to middle section 62.
- proof mass assembly 14 accelerates in the first direction 58, proof mass 22 may exert a downwards force on a top end of middle section 62, causing a width 66 of middle section 62 to decrease (e.g., compress) and causing a length 70 of middle section 62 to increase (e.g., stretch).
- the decrease in the width 66 of middle section 62 causes a decrease in a width 68 of resonator beam 20 and the increase in the length 70 of middle section 62 causes an increase in a length 72 of resonator beam 20.
- the increase in the length 70 of middle section 62 applies tension force 58' to resonator beam 20, resulting in the increase in the length 72 of resonator beam 20.
- proof mass 22 may exert an upwards force on a top end of middle section 62, causing the width 66 of middle section 62 to increase (e.g., stretch) and causing the length 70 of middle section 62 to decrease (e.g., compress). Since resonator beam 20 is connected to middle section 62, the increase in the width 66 of middle section 62 causes an increase in a width 68 of resonator beam 20 and the decrease in the length 70 of middle section 62 causes a decrease in a length 72 of resonator beam 20. For example, the decrease in the length 70 of middle section 62 applies compression force 60' to resonator beam 20, resulting in the decrease in the length 72 of resonator beam 20.
- first optical signal 44 may include TE light which induces a mechanical vibration of resonator beam 20 according to a TE resonance frequency mode.
- second optical signal 48 may include TM light which induces a mechanical vibration of resonator beam 20 according to a TM resonance frequency mode.
- the TE resonance frequency mode may represent a frequency distribution having one or more characteristics including a TE resonance frequency value and the TM resonance frequency mode may represent a frequency distribution having one or more characteristics including a TM resonance frequency value.
- the TE resonance frequency value of resonator beam 20 and the TM resonance frequency value of resonator beam 20 may change in opposite directions. That is, in some cases, the TE resonance frequency value may increase while the TM resonance frequency decreases or the TE resonance frequency value decreases while the TM resonance frequency increases responsive to the application of tension force 58'.
- the TE resonance frequency value of resonator beam 20 and the TM resonance frequency value of resonator beam 20 may change in opposite directions. That is, in some cases, the TE resonance frequency value may increase while the TM resonance frequency decreases or the TE resonance frequency value decreases while the TM resonance frequency increases responsive to the application of compression force 60'.
- a difference between the TE resonance frequency value and the TM resonance frequency value may be correlated with a magnitude of an acceleration of proof mass assembly 14. For example, if a first difference between a first TE resonance frequency value and a first TM resonance frequency value corresponds to a first acceleration value and a second difference between a second TE resonance frequency value and a second TM resonance frequency value corresponds to a second acceleration value, the first acceleration may be greater than the second acceleration when the first difference is greater than the second difference.
- processing circuitry may determine a sign (e.g., positive or negative) of the acceleration of proof mass assembly 14 based on comparing the TE resonance frequency value with the TM resonance frequency value.
- the TE resonance frequency value increases and the TM resonance frequency value decreases responsive to a positive acceleration (e.g., acceleration in direction 58) of proof mass assembly 14, where the TE resonance frequency value and the TM resonance frequency value are nearly the same while acceleration is zero.
- the TE resonance frequency value may decrease, and the TM resonance frequency value may increase responsive to a negative acceleration (e.g., acceleration in direction 60) of proof mass assembly 14.
- processing circuitry 12 may determine that the acceleration of proof mass assembly 14 is positive in response to determining that the TE resonance frequency value is greater than the TM resonance frequency value. By the same token, processing circuitry 12 may determine that the acceleration of proof mass assembly 14 is negative in response to determining that the TE resonance frequency value is less than the TM resonance frequency value.
- proof mass assembly 14 it may be beneficial to deposit a first thickness of a low-index dielectric material on a wafer of material, and deposit a second thickness of a second, high-index material on the waver. It may be possible fabricate a waveguide using lithography and etching techniques and create a linear resonator beam 20 using high-index material. Subsequently, it may be possible to then clad the waveguide and the resonator beam 20 with a second layer of the low-index dielectric material. A second conventional lithography and etching process may release proof mass 22 and the anchor (e.g., base section 64) from a substrate. In some examples, proof mass assembly 14 may include conventional fabrication of a microheater above resonator beam 20 to stabilize the accelerometer with respect to temperature.
- FIG. 3 is a conceptual diagram illustrating a resonator beam 100, in accordance with one or more techniques of this disclosure.
- resonator beam 100 is an example of resonator beam 20 of FIGS. 1 and 2 .
- resonator beam 100 includes a first oscillating edge 102 including a peak 104 and a second oscillating edge 112 including a valley 114.
- Resonator beam 100 may extend along a longitudinal axis 124 from a first end 132 to a second end 134.
- resonator beam 100 may receive one or more optical signals at first end 132 from a first circulator (e.g., first circulator 26 of FIG. 1 ) and resonator beam 100 may receive one or more optical signals at second end 134 from a second circulator (e.g., second circulator 34 of FIG. 1 ).
- first circulator e.g., first circulator 26 of FIG. 1
- second circulator 34 e.g., second circulator 34 of FIG. 1
- one or more sinusoidal functions may represent each of first oscillating edge 102 and second oscillating edge 112 (collectively, "oscillating edges 102, 112"). In this way, each of oscillating edges 102, 112 may resemble an oscillating pattern. Additionally, in some examples, one or more other functions (e.g., square functions, triangle functions, exponential functions, linear functions, polynomial functions, quadratic functions, or any combination thereof) may represent each of oscillating edges 102, 112. The one or more functions may be continuous (e.g., analog) or discrete (e.g., digital) in nature.
- resonator beam 20 may act as a reflective waveguide, allowing optical signals within one or more frequency bands to propagate through resonator beam 20, and "reflecting" optical signals within one or more other frequency bands.
- Oscillating edges 102, 112 may define the optical frequency bands which resonator beam 20 reflects and the frequency bands which resonator beam 20 allows to pass.
- the first oscillating edge 102 may cause the resonator beam 100 to be associated with a first spatial frequency
- the second oscillating edge 112 may cause the resonator beam 100 to be associated with a second spatial frequency, where the first spatial frequency and the second spatial frequency represent a first resonance frequency and a second resonance frequency, respectively.
- the first resonance frequency may represent a resonance frequency of resonator beam 100 induced by a first light mode (e.g., the TE light mode) and the second resonance frequency may represent a resonance frequency of resonator beam 100 induced by a second light mode (e.g., the TM light mode).
- a first light mode e.g., the TE light mode
- a second light mode e.g., the TM light mode
- a pi phase shift may exist between the oscillation pattern of first oscillating edge 102 and the oscillation pattern of second oscillating edge 112 relative to longitudinal axis 124.
- peak 104 of first oscillating edge 102 may be located at the same position 126 along longitudinal axis 124 as valley 114 of second oscillating edge 112.
- each peak of first oscillating edge 102 may be aligned with a respective valley of second oscillating edge 112 along longitudinal axis 124.
- resonator beam 100 may allow a first band of frequencies of a first modulated optical signal to propagate along the length of resonator beam 100 from first end 132 to second end 134 and allow a second band of frequencies of a second modulated optical signal to propagate along the length of resonator beam 100 from second end 134 to second end 132.
- Resonator beam 20 may reflect frequencies of the first modulated optical signal that are outside of the first frequency band back out of first end 132 and reflect frequencies of the second modulated optical signal that are outside of the second frequency band back out of second end 134.
- the portion of the first modulated optical signal which passes through resonator beam 20 may indicate the first resonance frequency and the portion of the second modulated optical signal which passes through resonator beam 20 may indicate the second resonance frequency.
- the first resonance frequency and the second resonance frequency may be identified based on frequencies that are present in the respective passed modulated optical signals.
- a compression force or a tension force applied to ends 132, 134 of resonator beam 100 may affect the first resonance frequency and the second resonance frequency of resonator beam 100.
- a proof mass assembly e.g., proof mass assembly 14 of FIG. 2
- a magnitude of a difference between the first resonance frequency and the second resonance frequency caused by the force applied to ends 132, 134 indicates the magnitude of the acceleration of the proof mass assembly.
- the width 122 of resonator beam 100 may be within a range from 200 nanometers (nm) to 700 nm (e.g., 500 nm), but this is not required.
- the width 122 of resonator beam 100 may include any width or range of widths.
- a length 123 of resonator beam 100 may be within a range from 1 millimeter (mm) to 5mm, but this is not required.
- the length 123 of resonator beam 100 may include any length or range of lengths.
- Resonator beam 100 is not meant to be limited to the oscillating pattern of first oscillating edge 102 and the oscillating pattern of second oscillating edge 112 which are illustrated in FIG. 3 .
- First oscillating edge 102 may include more periods than are illustrated in FIG. 3 or less periods than are illustrated in FIG. 3 in some cases.
- second oscillating edge 112 may include more periods than are illustrated in FIG. 3 or less periods than are illustrated in FIG. 3 in some cases.
- FIG. 4 is a graph illustrating a first frequency plot 142 and a second frequency plot 144, in accordance with one or more techniques of this disclosure.
- first frequency plot 142 includes a first peak frequency 146 and second frequency plot 144 includes a second peak frequency 148.
- First peak frequency 146 and second peak frequency 148 are separated by a frequency difference value 150.
- the first frequency plot 142 includes one or more frequency components of the modulated first optical signal 44 which is delivered to the first end 52 of resonator beam 20.
- First frequency plot 142 may represent a distribution of frequencies which propagate through resonator beam 20 from first end 52 to second end 54. Since photoreceiver 28 receives the passed first optical signal 45 which includes frequency components passed by resonator beam 20, the first frequency plot 142 may represent one or more frequency components which are present in the passed first optical signal 45.
- the first peak frequency 146 may represent a first resonance frequency in which resonator beam 20 mechanically vibrates.
- the second frequency plot 144 includes one or more frequency components of the modulated second optical signal 48 which is delivered to the second end 54 of resonator beam 20.
- Second frequency plot 144 may represent a distribution of frequencies which propagate through resonator beam 20 from second end 54 to first end 52. Since photoreceiver 28 receives the passed second optical signal 49 which includes frequency components passed by resonator beam 20, the second frequency plot 144 may represent one or more frequency components which are present in the passed second optical signal 49.
- the second peak frequency 148 represents a second resonance frequency in which resonator beam 20 mechanically vibrates.
- Processing circuitry 12 of FIG. 1 may be configured to determine an acceleration of accelerometer system 10 based on the frequency difference value 150, which represents a difference between the first peak frequency 146 and the second peak frequency 148.
- a linear or near-linear relationship may exist between a magnitude of the acceleration of accelerometer system 10 and a magnitude of the difference between the first peak frequency 146 and the second peak frequency 148. For example, if the acceleration increases, the frequency difference value 150 may also increase by a similar proportion and if the acceleration decreases, the frequency difference value 150 may also decrease.
- the first frequency plot 142 may represent one or more frequencies of TE light and the second frequency plot 144 may represent one or more frequencies of TM light, but this is not required. In some examples, the first frequency plot 142 and the second frequency plot 144 may be associated with other types of light.
- the first resonance frequency may represent a frequency in which resonator beam 20 vibrates according to a TE resonance frequency mode and the second resonance frequency may represent a frequency in which resonator beam 20 vibrates according to a TM resonance frequency mode.
- FIG. 5 is a flow diagram illustrating an example operation for determining an acceleration using an opto-mechanical resonator beam, in accordance with one or more techniques of this disclosure.
- FIG. 5 is described with respect to accelerometer system 10, proof mass assembly 14, circuit 16, and resonator beam 100 of FIGS. 1-4 .
- the techniques of FIG. 5 may be performed by different components of accelerometer system 10, proof mass assembly 14, circuit 16, and resonator beam 100 or by additional or alternative devices.
- processing circuitry 12 may be configured to determine an acceleration of accelerometer system 10.
- the accelerometer system 10 may include a resonator beam 20 which is configured to mechanically vibrate according to a first resonance frequency and a second resonance frequency.
- resonator beam 20 may represent an opto-mechanical resonator beam configured to act as an optical waveguide for two or more types of light (e.g., TE light and TM light).
- Processing circuitry 12 may determine acceleration based on a difference between the first resonance frequency and the second resonance frequency.
- First light-emitting device 24 may emit a first optical signal 44' to first modulator 25 (502).
- first modulator 25 may generate a modulated first optical signal 44 to include TE light in order to induce a mechanical vibration in resonator beam 20 according to a TE resonance frequency mode.
- First modulator 25 may output the modulated first optical signal 44 to resonator 20 via first circulator 26 (504).
- first circulator 26 directs the modulated first optical signal 44 to a first end 52 of resonator beam 20 via one or more optical fibers. A portion of the modulated first optical signal 44 may travel through resonator 20 form first end 52 to second end 54.
- This portion of the modulated first optical signal 44 may include a band of frequencies which corresponds to a resonance frequency of resonator 20.
- Photoreceiver 28 may receive passed first optical signal 45 from resonator beam 20 (506) via a second circulator 34.
- the passed first optical signal 45 may include one or more frequency components of modulated first optical signal 44 which are passed by resonator beam 20 which correspond to the resonance frequency.
- processing circuitry 12 may generate an error signal.
- the error signal may reflect any detectable difference between the modulated first optical signal 44 and the passed first optical signal 45.
- first light-emitting device 24 may emit first optical signal 44' to include frequency components representative of the first resonance frequency of resonator 20. Any frequency components of the first optical signal 44' may be reflected by resonator beam 20.
- Photoreceiver 28 may receive the reflected first optical signal 46 and processing circuitry 12 may generate the error signal based on the reflected first optical signal 46.
- Processing circuitry 12 outputs the error signal to first light-emitting device 24 (508) in order to control first light-emitting device 24 to generate first optical signal 44' such that first optical signal 44' does not include frequencies outside of the first resonance frequency.
- photoreceiver 28 In response to receiving the passed first optical signal 45, photoreceiver 28 generates an electrical signal based on the first resonant frequency of resonator beam 20 (510), which is indicated by the passed first optical signal 45 received by photoreceiver 48. Photoreceiver 28 outputs the electrical signal to processing circuitry 12. Processing circuitry 12 may determine the acceleration of accelerometer system 10 based on the electrical signal (512).
- accelerometer system 10 includes a second feedback loop which delivers another optical signal to photoreceiver 28, the other optical signal indicating the second resonance frequency of resonator beam 20.
- Processing circuitry 12 may determine the acceleration based on the difference between the first resonance frequency and the second resonance frequency.
- the accelerometers described herein may utilize hardware, software, firmware, or any combination thereof for achieving the functions described.
- Those functions implemented in software may be stored on or transmitted over, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit.
- Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol.
- computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave.
- Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure.
- processors may be executed by one or more processors within the accelerometer or communicatively coupled to the accelerometer.
- the one or more processors may, for example, include one or more DSPs, general purpose microprocessors, application specific integrated circuits ASICs, FPGAs, or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor,” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein.
- the functionality described herein may be provided within dedicated hardware and/or software modules configured for performing the techniques described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements.
- ICs integrated circuits
- chip sets e.g., chip sets
- Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, various units may be combined or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Gyroscopes (AREA)
- Micromachines (AREA)
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Description
- This disclosure relates to accelerometers.
- Accelerometers function by detecting a displacement of a proof mass under inertial forces. In one example, an accelerometer may detect the displacement of a proof mass by the change in frequency of a resonator connected between the proof mass and a support base. A resonator may be designed to change frequency proportional to the load applied to the resonator by the proof mass under acceleration. The resonator may be electrically coupled to oscillator circuitry, or other signal generation circuitry, which causes the resonator to vibrate at a resonance frequency.
-
EP3112879A1 discloses systems, devices, techniques, and methods for an opto-mechanical vibrating beam accelerometer. In one example, a system is configured to couple a laser into optical resonance with opto-mechanically active (OMA) anchors suspending a proof mass. The system measures an acceleration based on instantaneous resonance frequencies of the OMA anchors through changes to the amplitude or phase of the modulated laser. -
US10705112B1 - The present invention is defined by the independent claims, to which reference should now be made. Advantageous embodiments are set out in the dependent claims.
- The summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the systems, device, and methods described in detail within the accompanying drawings and description below. Further details of one or more examples of this disclosure are set forth in the accompanying drawings and in the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
-
-
FIG. 1 is a block diagram illustrating an accelerometer system, in accordance with one or more techniques of this disclosure. -
FIG. 2 is a block diagram illustrating a proof mass assembly and a circuit, in accordance with one or more techniques of this disclosure. -
FIG. 3 is a conceptual diagram illustrating a resonator beam, in accordance with one or more techniques of this disclosure. -
FIG. 4 is a graph illustrating a first frequency plot and a second frequency plot, in accordance with one or more techniques of this disclosure. -
FIG. 5 is a flow diagram illustrating an example operation for determining an acceleration using an opto-mechanical resonator beam, in accordance with one or more techniques of this disclosure. - Like reference characters denote like elements throughout the description and figures.
- This disclosure is directed to devices, systems and techniques for determining an acceleration of a vibrating beam accelerometer (VBA). For example, the disclosure is directed to a VBA with a proof mass, a base section, and a resonator beam. The resonator beam may be configured to receive a first optical signal and a second optical signal, which induce the resonator to vibrate at a first resonance frequency and a second resonance frequency, respectively. The respective magnitudes of resonance frequencies of the resonator beam may indicate the acceleration of the VBA. That is, the first resonance frequency and the second resonance frequency may change based on the acceleration of the VBA and it may be possible to determine the acceleration of the VBA based on the first resonance frequency and the second resonance frequency.
- In some examples, a first negative feedback loop may control a first light-emitting device to emit the first optical signal at the first resonance frequency and a second negative feedback loop control a second light-emitting device to emit the second optical signal at the second resonance frequency. For example, the resonator may pass a first portion of the first optical signal and reflect a second portion of the first optical signal. Additionally, the resonator may pass a first portion of the second optical signal and reflect a second portion of the second optical signal. The first portion of the first optical signal may represent a portion of the first optical signal representing the first resonance frequency and the first portion of the second optical signal may represent the portion of the second resonance frequency representing the second resonance frequency. The reflected portions of the first optical signal and the second optical signals, on the other hand, may represent portions that do not represent the first resonance frequency and the second resonance frequency, respectively. As such, the processing circuitry may generate a first error signal to adjust the first optical signal emitted by the first light-emitting device in order to eliminate frequencies other than the first resonance frequency and the processing circuitry may generate a second error signal to adjust the second optical signal emitted by the second light-emitting device in order to eliminate frequencies outside of the second resonance frequency
- A photoreceiver (e.g., a photodiode) may receive the first portion of the first optical signal, the second portion of the first optical signal, the first portion of the second optical signal, and the second portion of the second optical signal. The photoreceiver may generate one or more electrical signals which represent the optical signals received by the photoreceiver and output the one or more electrical signals to the processing circuitry. The processing circuitry may generate the first error signal based on the first portion of the first optical signal and generate the second error signal based on a first portion of the second optical signal. The processing circuitry may output the first error signal to the first light-emitting device in order to regulate the first optical signal to represent the first resonance frequency and the processing circuitry may output the second error signal to the second light-emitting device in order to regulate the second optical signal to represent the second resonance frequency.
- The processing may determine the acceleration of the VBA based on the first resonance frequency indicated by the first portion of the first optical signal and the second resonance frequency indicated by the first portion of the second optical signal. For example, a relationship may exist between a difference between a magnitude of the first resonance frequency of the resonator and a magnitude of the second resonance frequency of the resonator and the acceleration of the VBA. As such, the processing circuitry may calculate the acceleration of the VBA based on a difference between the first and second resonance frequencies of the resonator.
- The techniques of this disclosure may provide one or more advantages. For example, readout signals of some accelerometers may be compromised by environmental factors such as temperature. It may be the case that a sole resonance frequency component of a resonator is affected by a temperature of an environment proximate to the VBA, thus affecting an acceleration which is measured based on one resonance frequency of one light mode. One or more techniques of this disclosure include determining an acceleration of a VBA based on a difference between two or more resonance frequencies, each resonance frequency of the two or more resonance frequencies corresponding to a different light mode. Environmental factors may affect each resonance frequency of the two or more resonance frequencies by substantially the same amount, thus eliminating an impact of the environmental factors on the measured acceleration. For example, when acceleration is measured based on a difference between a first resonance frequency and a second resonance frequency, a change in temperature may cause both of the first resonance frequency and the second resonance frequency to change by the same amount while acceleration remains constant. In this way, the difference between the first resonance frequency and the second resonance frequency remains the same, which means that the measured acceleration remains the same.
-
FIG. 1 is a block diagram illustrating anaccelerometer system 10, in accordance with one or more techniques of this disclosure. As illustrated inFIG. 1 ,accelerometer system 10 includesprocessing circuitry 12,resonator beam 20,proof mass 22, first light-emitting device 24,first modulator 25,first circulator 26,photoreceiver 28, second light-emitting device 32, second modulator, and second circulator 34. -
Accelerometer system 10 is configured to determine an acceleration based on two or more measured resonance frequencies ofresonator beam 20, which is mechanically connected toproof mass 22. For example,proof mass 22 may be capable of applying one or both of a compression force and a tension force toresonator beam 20, affecting the two or more resonance frequencies used to determine the acceleration. For example, asproof mass 22 changes a force applied toresonator beam 20, a first resonance frequency and a second resonance frequency may each change based on the change a magnitude of the force applied toresonator beam 20 byproof mass 22, where the change in the magnitude of the force is correlated with a change in the acceleration ofaccelerometer system 10. In some examples,accelerometer system 10 may calculate the acceleration based on the difference between the first resonance frequency mode and the second resonance frequency mode. -
Processing circuitry 12 may include one or more processors that are configured to implement functionality and/or process instructions for execution withinaccelerometer system 10. For example,processing circuitry 12 may be capable of processing instructions stored in a memory.Processing circuitry 12 may include, for example, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or equivalent discrete or integrated logic circuitry, or a combination of any of the foregoing devices or circuitry. Accordingly,processing circuitry 12 may include any suitable structure, whether in hardware, software, firmware, or any combination thereof, to perform the functions ascribed herein to processingcircuitry 12. - A memory (not illustrated in
FIG. 1 ) may be configured to store information withinaccelerometer system 10 during operation. The memory may include a computer-readable storage medium or computer-readable storage device. In some examples, the memory includes one or more of a short-term memory or a long-term memory. The memory may include, for example, random access memories (RAM), dynamic random access memories (DRAM), static random access memories (SRAM), magnetic discs, optical discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable memories (EEPROM). In some examples, the memory is used to store program instructions for execution by processingcircuitry 12. -
Resonator beam 20 may represent a mechanical beam which is located betweenproof mass 22 and a base section (not illustrated inFIG. 1 ).Proof mass 22, in some cases, may apply a tension force toresonator beam 20 or apply a compression force toresonator beam 20. In some examples, resonator beam may be configured to mechanically vibrate according to two or more resonance frequencies, Whenproof mass 22 applies a tension force toresonator beam 20 in response to an acceleration in afirst direction 58, the tension force may "pull" onfirst end 52 andsecond end 54 ofresonator beam 20 and a magnitude of each resonance frequency of the one or more resonance frequencies may change by a predetermined amount corresponding to a magnitude of the tension force. Alternatively, whenproof mass 22 applies a compression force toresonator beam 20 in response to an acceleration in asecond direction 60, the compression force may "push" onfirst end 52 andsecond end 54 ofresonator beam 20 and the magnitude of each resonance frequency of the two or more resonance frequencies may change by a predetermined amount corresponding to a magnitude of the compression force. - In this way, tension forces and compression forces applied to
resonator beam 20 responsive to acceleration in thefirst direction 58 and thesecond direction 60, respectively, may affect characteristics (e.g., magnitude) of the two or more resonance frequencies by whichresonator beam 20 vibrates. Measuring the magnitude and the sign (e.g., positive or negative) of each resonance frequency of the two or more resonance frequencies may allow processingcircuitry 12 to determine a magnitude and a sign of the acceleration ofaccelerometer system 10. For example, processingcircuitry 12 may determine the acceleration based on one or more electrical signals generated byphotoreceiver 28, which indicate the difference between a first resonance frequency ofresonator 20 and a second resonance frequency ofresonator 20. - First light-emitting
device 24 and second light-emitting device 32 (collectively, "light-emittingdevices devices device 24 is a first semiconductor laser which includes a first laser diode and second light-emittingdevice 32 is a second semiconductor laser which includes a second laser diode. First light-emittingdevice 24 may generate a first optical signal 44' based on a first error signal received from processingcircuitry 12. Second light-emittingdevice 32 may generate a second optical signal 48' based on a second error signal received from processingcircuitry 12. -
First modulator 25 and second modulator 33 (collectively, "modulators device 24 and the second light-emittingdevice 32, respectively.First modulator 25, for example, may receive first optical signal 44' from first light-emittingdevice 24 whilefirst modulator 25 also receives a first modulator control signal from a first control unit (not illustrated inFIG. 1 ) which regulates a manner in whichfirst modulator 25 modulates the first optical signal.First modulator 25, in some cases, may transmit a modulated firstoptical signal 44 tofirst circulator 26. Additionally,second modulator 33 may receive second optical signal 48' from second light-emittingdevice 32 whilesecond modulator 33 also receives a second modulator control signal from a second control unit (not illustrated inFIG. 1 ) which regulates a manner in whichsecond modulator 33 modulates the second optical signal.Second modulator 33, in some cases, may transmit a modulated secondoptical signal 48 to second circulator 34. -
First circulator 26 and second circulator 34 (collectively, "circulators 26, 34") may represent optical devices configured to receive optical signals via one or more optical inputs and output optical signals via one or more optical outputs. For example,first circulator 26 includes first optical inputs 36A-36C (collectively, "first optical inputs 36") andfirst circulator 26 also includes firstoptical outputs 38A-38C (collectively, "first optical outputs 38"). Second circulator 34 includes second optical inputs 40A-40C (collectively, "second optical inputs 40") and second circulator 34 also includes secondoptical outputs 42A-42C (collectively, "optical outputs 42"). - First light-emitting
device 24 generates a first optical signal 44' and outputs the first optical signal 44' tofirst modulator 25.First modulator 25 modulates the first optical signal 44' in order to generate a modulated firstoptical signal 44. In some examples,first modulator 25 receives a first modulator control signal which causesfirst modulator 25 to generate modulated firstoptical signal 44 according to a first light mode.First modulator 25 outputs the modulated firstoptical signal 44 tofirst circulator 26 via optical input 36A.First circulator 26 may direct modulated firstoptical signal 44 to afirst end 52 ofresonator beam 20 viaoptical output 38A. The modulated firstoptical signal 44 may travel throughresonator beam 20 to a position proximate acenter 56 ofresonator beam 20. In some examples, modulated firstoptical signal 44 may include a range of optical frequencies.Resonator beam 20 may reflect some optical frequencies of modulated firstoptical signal 44 and allow some optical frequencies of modulated firstoptical signal 44 to pass through the length ofresonator beam 20 fromfirst end 52 tosecond end 54. -
Resonator beam 20 may reflect a first portion of modulated firstoptical signal 44 and allow a second portion of modulated firstoptical signal 44 to pass throughresonator beam 20 from thefirst end 52 to thesecond end 54. The second portion of modulated firstoptical signal 44 which exits thesecond end 54 ofresonator beam 20 may represent a "passed" firstoptical signal 45.Resonator beam 20 may reverse a direction of the first portion of the modulated firstoptical signal 44 which is reflected, causing the first portion of the modulated firstoptical signal 44 to exit at thefirst end 52 ofresonator beam 20. As such, the optical signal exiting thefirst end 52 ofresonator beam 20 may represent a "reflected" firstoptical signal 46. In some examples, the first portion of modulated firstoptical signal 44 includes one or more bands of frequencies and the second portion of modulated firstoptical signal 44 represents a narrow band of frequencies which indicate a first resonance frequency ofresonator beam 20. - The first lighting mode of the modulated first
optical signal 44 may, in some cases, represent a Transverse Electric (TE) lighting mode. Light which propagates according to the TE lighting mode may be referred to herein as "TE Light." TE light represents light which does not induce an electric field in a direction of propagation and does induce a magnetic field in the direction of propagation. For example, as modulated firstoptical signal 44 propagates from thefirst end 52 ofresonator beam 20 towards thecenter 56 ofresonator beam 20, modulated firstoptical signal 44 induces a magnetic field in a horizontal direction (e.g., the direction alongresonator beam 20 from thefirst end 52 to the second end 54) relative toresonator beam 20 and does not induce an electric field in the horizontal direction. The TE light of modulated firstoptical signal 44 may causeresonator beam 20 to vibrate mechanically at a first resonance frequency which corresponds to the TE lighting mode. The passed firstoptical signal 45 may, in turn, indicate the first resonance frequency ofresonator beam 20.First circulator 26 may receive the reflected firstoptical signal 46 viaoptical input 36B. Then,first circulator 26 outputs the reflected firstoptical signal 46 tophotoreceiver 48 viaoptical output 38B. - Second light-emitting
device 32 generates a second optical signal 48' and outputs the second optical signal 48' tosecond modulator 33.Second modulator 33 modulates the second optical signal 48' in order to generate a modulated secondoptical signal 48. In some examples,second modulator 33 receives a second modulator control signal which causessecond modulator 33 to generate modulated secondoptical signal 48 according to a second light mode.Second modulator 33 outputs the modulated secondoptical signal 48 to second circulator 34 via optical input 40A. Second circulator 34 may direct modulated secondoptical signal 48 to thesecond end 54 ofresonator beam 20 viaoptical output 42A. The modulated secondoptical signal 48 may travel throughresonator beam 20 to a position proximate acenter 56 ofresonator beam 20. In some examples, modulated secondoptical signal 48 may include a range of optical frequencies.Resonator beam 20 may reflect some optical frequencies of modulated secondoptical signal 48 and allow some optical frequencies of modulated secondoptical signal 48 to pass through the length ofresonator beam 20 fromsecond end 54 tofirst end 52. -
Resonator beam 20 may reflect a first portion of modulated secondoptical signal 48 and allow a second portion of modulated secondoptical signal 48 to pass throughresonator beam 20 from thesecond end 54 to thefirst end 52. The second portion of modulated secondoptical signal 48 which exits thefirst end 52 ofresonator beam 20 may represent a "passed" secondoptical signal 49.Resonator beam 20 may reverse a direction of the first portion of the modulated secondoptical signal 48 which is reflected, causing the first portion of the modulated secondoptical signal 48 to exit at thesecond end 54 ofresonator beam 20. As such, the optical signal exiting thesecond end 54 ofresonator beam 20 may represent a "reflected" secondoptical signal 50. In some examples, the first portion of modulated secondoptical signal 48 includes one or more bands of frequencies and the second portion of modulated secondoptical signal 48 represents a narrow band of frequencies which indicate a second resonance frequency ofresonator beam 20. - The second lighting mode of the modulated second
optical signal 48 may, in some cases, represent a Transverse Magnetic (TM) lighting mode. Light which propagates according to the TM lighting mode may be referred to herein as "TM Light." TM light represents light which does not induce a magnetic field in a direction of propagation and does induce an electric field in the direction of propagation. For example, as modulated secondoptical signal 48 propagates from thesecond end 54 ofresonator beam 20 towards thecenter 56 ofresonator beam 20, modulated secondoptical signal 48 induces an electrical field in a horizontal direction (e.g., the direction alongresonator beam 20 from thesecond end 54 to the first end 52) relative toresonator beam 20 and does not induce a magnetic field in the horizontal direction. The TM light of modulated secondoptical signal 48 may causeresonator beam 20 to vibrate mechanically at a second resonance frequency which corresponds to the TM lighting mode. The passed secondoptical signal 49 may, in turn, indicate the second resonance frequency ofresonator beam 20. Second circulator 34 may receive the reflected secondoptical signal 50 viaoptical input 40B. Then, second circulator 34 outputs the reflected secondoptical signal 50 tophotoreceiver 48 via optical output 42B. -
First circulator 26 may receive passed secondoptical signal 49 viaoptical input 36C and forward passed secondoptical signal 49 tophotoreceiver 28 viaoptical output 38C.Second circulator 33 may receive passed firstoptical signal 45 viaoptical input 40C and forward passed firstoptical signal 45 tophotoreceiver 28 via optical output 42C. Although modulated firstoptical signal 44 is described herein as including TE light and modulated secondoptical signal 48 is described herein as including TM light, this is not required. In some examples, modulated firstoptical signal 44 includes TM light and modulated secondoptical signal 48 may include TE light. In some examples, firstoptical signal 44 and secondoptical signal 48 may include one or more other types of light which causeresonator beam 20 to mechanically vibrate according to two different modes. - In general,
photoreceiver 28 may include one or more transistors configured to absorb photons of one or more optical signals and output, in response to absorbing the photons, an electrical signal. In this manner,photoreceiver 28 may be configured to convert optical signals into electrical signals.Photoreceiver 20 receives the passed firstoptical signal 45, the reflected firstoptical signal 46, the passed secondoptical signal 49, and the reflected secondoptical signal 50.Photoreceiver 28, for example, may include one or more p-n junctions that convert the photons of one or more optical signals into corresponding electrical signals. - For example,
photoreceiver 28 may generate a first electrical signal component based on the passed firstoptical signal 45 and generate a second electrical signal component based on the passed secondoptical signal 49. The first electrical signal component may preserve at least some of the parameters of passed firstoptical signal 45 and the second electrical signal component may preserve at least some of the parameters of passed secondoptical signal 49. For example, the first electrical signal component may indicate the first resonance frequency (e.g., the TE resonance frequency) which is indicated by the passed firstoptical signal 45. The second electrical signal component may indicate the second resonance frequency (e.g., the TM resonance frequency) which is indicated by the passed secondoptical signal 49. - One or more frequency values and intensity values associated with passed first
optical signal 45 and passed secondoptical signal 49 may be indicated by the first electrical signal component and the second electrical signal component, respectively. For example,photoreceiver 28 may produce a stronger electrical signal (i.e., greater current magnitude) in response to receiving a stronger (e.g., greater power) optical signal.Photoreceiver 28 may include semiconductor materials such as any one or combination of Indium Gallium Arsenide, Silicon, Silicon Carbide, Silicon Nitride, Gallium Nitride, Germanium, or Lead Sulphide. - A difference between the TE resonance frequency and the TM resonance frequency might, in some cases, be correlated with an acceleration of
accelerometer system 10. For example, a first difference between the TE resonance frequency and the TM resonance frequency may represent a first acceleration and a second difference between the TE resonance frequency, and the TM resonance frequency may represent a second acceleration. When the first difference is greater than the second difference, the first acceleration may be greater than the second acceleration. Alternatively, when the first difference is less than the second difference, the first acceleration may be less than the second acceleration. - There may be a substantially linear relationship between the difference between the TE resonance frequency and the TM resonance frequency and the acceleration of
accelerometer system 10, but this is not required. For example, the relationship between the difference and the acceleration may be modelled by an equation that is nearly linear but includes one or more quadratic coefficients introducing slight nonlinear irregularities. In any case, processingcircuitry 12 may be configured to apply the relationship in order to calculate the acceleration ofaccelerometer system 10 based on the difference between the TE resonance frequency and the TM resonance frequency indicated by the electrical signal. - It may be more beneficial to determine the acceleration of
accelerometer system 10 based on the difference between the TE resonance frequency and the TM resonance frequency as compared with accelerometer systems which determine acceleration based solely on a measured resonance frequency value. For example, the difference between TE resonance frequency and the TM resonance frequency is a difference between two frequency values and does not represent a single frequency magnitude value. In some examples, environmental factors such as a temperature in an area proximate to theaccelerometer system 10 may affect the TE resonance frequency and the TM resonance frequency by the same or similar factors, meaning that the difference between the TE resonance frequency and the TM resonance frequency is not substantially affected by these environmental factors, which is beneficial. - Additionally, it may be beneficial for the TE resonance frequency and the TM resonance frequency to not be the same while the acceleration of
accelerometer system 10 is zero. For example, it may be easier to determine a difference between a positive acceleration ofaccelerometer system 10 and a negative acceleration ofaccelerometer system 10 when a difference between the TE resonance frequency and the TM resonance frequency is not the same while the acceleration ofaccelerometer system 10 is zero. - In some examples, processing
circuitry 12 is configured to generate a first error signal for output to first light-emittingdevice 24. In some examples, processingcircuitry 12 generates the first error signal in order to cause first light-emittingdevice 24 to generate first optical signal 44' to include one or more frequency components corresponding to the first resonance frequency ofresonator 20.Resonator 20 may reflect any portions of the first modulatedoptical signal 44 which are outside of the narrow band of frequencies which represent the first resonance frequency. These reflected portions are represented by reflected firstoptical signal 46.Processing circuitry 12 may generate the first error signal based on one or more parameters of the reflected firstoptical signal 46 in order to cause an entirety of modulated firstoptical signal 44 to pass throughresonator 20. In other words, when the error signal is equal to zero, a magnitude of reflected firstoptical signal 46 is zero and an entirety of modulated firstoptical signal 44 passes throughresonator 20. - In some examples, processing
circuitry 12 is configured to generate a second error signal for output to second light-emittingdevice 32. In some examples, processingcircuitry 12 generates the second error signal in order to cause second light-emittingdevice 32 to generate second optical signal 48' to include one or more frequency components corresponding to the second resonance frequency ofresonator 20.Resonator 20 may reflect any portions of the second modulatedoptical signal 48 which are outside of the narrow band of frequencies which represent the second resonance frequency. These reflected portions are represented by reflected secondoptical signal 50.Processing circuitry 12 may generate the second error signal based on one or more parameters of the reflected secondoptical signal 50 in order to cause an entirety of modulated secondoptical signal 48 to pass throughresonator 20. In other words, when the error signal is equal to zero, a magnitude of reflected secondoptical signal 50 is zero and an entirety of modulated secondoptical signal 48 passes throughresonator 20. - In some examples,
accelerometer system 10 may only allow the measurement of an acceleration along a single proof mass displacement axis, thus allowingaccelerometer system 10 to measure acceleration along one Cartesian axis only. In some examples, the proof mass displacement axis ofaccelerometer system 10 is parallel tofirst direction 58 and parallel tosecond direction 60. For example, whenproof mass 22 is "displaced" closer toresonator beam 20 along the proof mass displacement axis, this may cause a tension force to be applied toresonator beam 20 which in turn causes resonance frequency modes to shift proportional to the acceleration ofproof mass 22. In some cases, to obtain an acceleration of an object relative to all three Cartesian axes, three accelerometer systems are placed on the object such that the proof mass displacement axes of the respective accelerometer systems are aligned to form an x-axis, a y-axis, and a z-axis of a Cartesian space. As such, readouts from each of the three accelerometer systems may be combined to determine a three-dimensional acceleration vector. -
Accelerometer system 10 is configured to measure the acceleration of the object in real-time or near real-time. Since processingcircuitry 12 determines one or more resonance frequencies ofresonator beam 20 based on optical signals which travel at the speed of light, processingcircuitry 12 may be configured to determine the acceleration ofaccelerometer system 10 within a very short latency period (e.g., less than one nanosecond (ns)). In other words, processingcircuitry 12 may determine the acceleration ofaccelerometer system 10 at a time that is very close to a present time, such as a time less than one nanosecond preceding the present time. - It may be beneficial to track acceleration in real time or near real-time in order to determine a positional displacement of an object during a period of time. For example,
accelerometer system 10 may be a part of an inertial navigation system (INS) for tracking a position of an object based, at least in part, on an acceleration of the object. Additionally,accelerometer system 10 may be located on or within the object such thataccelerometer system 10 accelerates with the object. As such, when the object accelerates, accelerometer system 10 (includingproof mass 22 and resonator beam 20) accelerates with the object. Since acceleration over time is a derivative of velocity over time, and velocity over time is a derivative of position over time, processingcircuitry 12 may, in some cases, be configured to determine the position displacement of the object by performing a double integral of the acceleration of the object over the period of time. Determining a position of an object usingaccelerometer system 10 located on the object, and not using a navigation system separate from the object (e.g., a Global Positioning System (GPS)), may be referred to as "dead reckoning." -
FIG. 2 is a block diagram illustrating a proofmass assembly 14 and acircuit 16, in accordance with one or more techniques of this disclosure. As seen inFIG. 2 , proofmass assembly 14 includesproof mass 22,middle section 62, andbase section 64.Resonator beam 20 may be located on, within, or otherwise in contact withmiddle section 62.Circuit 16 may represent an opto-electrical circuit configured to emit one or more optical signals to proofmass assembly 14. In some examples,circuit 16 includesprocessing circuitry 12, first light-emittingdevice 24,first circulator 26,photoreceiver 28, second light-emittingdevice 32, and second circulator 34 ofFIG. 1 . - In some examples,
proof mass 22 is mechanically connected tomiddle section 62, andmiddle section 62 is mechanically connected tobase section 64.Proof mass 22 may apply one or both of compression forces and tension forces toresonator beam 20 by nature of being mechanically connected tomiddle section 62. For example, when proofmass assembly 14 accelerates in thefirst direction 58,proof mass 22 may exert a downwards force on a top end ofmiddle section 62, causing awidth 66 ofmiddle section 62 to decrease (e.g., compress) and causing alength 70 ofmiddle section 62 to increase (e.g., stretch). Sinceresonator beam 20 is connected tomiddle section 62, the decrease in thewidth 66 ofmiddle section 62 causes a decrease in awidth 68 ofresonator beam 20 and the increase in thelength 70 ofmiddle section 62 causes an increase in alength 72 ofresonator beam 20. For example, the increase in thelength 70 ofmiddle section 62 applies tension force 58' toresonator beam 20, resulting in the increase in thelength 72 ofresonator beam 20. - Additionally, in some cases, when proof
mass assembly 14 accelerates in thesecond direction 60,proof mass 22 may exert an upwards force on a top end ofmiddle section 62, causing thewidth 66 ofmiddle section 62 to increase (e.g., stretch) and causing thelength 70 ofmiddle section 62 to decrease (e.g., compress). Sinceresonator beam 20 is connected tomiddle section 62, the increase in thewidth 66 ofmiddle section 62 causes an increase in awidth 68 ofresonator beam 20 and the decrease in thelength 70 ofmiddle section 62 causes a decrease in alength 72 ofresonator beam 20. For example, the decrease in thelength 70 ofmiddle section 62 applies compression force 60' toresonator beam 20, resulting in the decrease in thelength 72 ofresonator beam 20. - An increase in the
length 72 ofresonator beam 20 caused by tension force 58' or a decrease in thelength 72 ofresonator beam 20 caused by compression force 60' may affect one or more resonance frequency modes ofresonator beam 20 which are induced by optical signals delivered toresonator beam 20 bycircuit 16. For example, firstoptical signal 44 may include TE light which induces a mechanical vibration ofresonator beam 20 according to a TE resonance frequency mode. Additionally, or alternatively, secondoptical signal 48 may include TM light which induces a mechanical vibration ofresonator beam 20 according to a TM resonance frequency mode. The TE resonance frequency mode may represent a frequency distribution having one or more characteristics including a TE resonance frequency value and the TM resonance frequency mode may represent a frequency distribution having one or more characteristics including a TM resonance frequency value. - In one or more examples where tension force 58' is applied to
resonator beam 20 causing thelength 72 ofresonator beam 20 to increase, the TE resonance frequency value ofresonator beam 20 and the TM resonance frequency value ofresonator beam 20 may change in opposite directions. That is, in some cases, the TE resonance frequency value may increase while the TM resonance frequency decreases or the TE resonance frequency value decreases while the TM resonance frequency increases responsive to the application of tension force 58'. Similarly, in one or more examples where compression force 60' is applied toresonator beam 20 causing thelength 72 ofresonator beam 20 to decrease, the TE resonance frequency value ofresonator beam 20 and the TM resonance frequency value ofresonator beam 20 may change in opposite directions. That is, in some cases, the TE resonance frequency value may increase while the TM resonance frequency decreases or the TE resonance frequency value decreases while the TM resonance frequency increases responsive to the application of compression force 60'. - A difference between the TE resonance frequency value and the TM resonance frequency value may be correlated with a magnitude of an acceleration of proof
mass assembly 14. For example, if a first difference between a first TE resonance frequency value and a first TM resonance frequency value corresponds to a first acceleration value and a second difference between a second TE resonance frequency value and a second TM resonance frequency value corresponds to a second acceleration value, the first acceleration may be greater than the second acceleration when the first difference is greater than the second difference. - In some examples, processing circuitry (e.g., processing
circuitry 12 ofFIG. 1 ) may determine a sign (e.g., positive or negative) of the acceleration of proofmass assembly 14 based on comparing the TE resonance frequency value with the TM resonance frequency value. In some cases, the TE resonance frequency value increases and the TM resonance frequency value decreases responsive to a positive acceleration (e.g., acceleration in direction 58) of proofmass assembly 14, where the TE resonance frequency value and the TM resonance frequency value are nearly the same while acceleration is zero. Additionally, in some cases, the TE resonance frequency value may decrease, and the TM resonance frequency value may increase responsive to a negative acceleration (e.g., acceleration in direction 60) of proofmass assembly 14. - In at least some such cases, processing
circuitry 12 may determine that the acceleration of proofmass assembly 14 is positive in response to determining that the TE resonance frequency value is greater than the TM resonance frequency value. By the same token, processingcircuitry 12 may determine that the acceleration of proofmass assembly 14 is negative in response to determining that the TE resonance frequency value is less than the TM resonance frequency value. - To fabricate proof
mass assembly 14, it may be beneficial to deposit a first thickness of a low-index dielectric material on a wafer of material, and deposit a second thickness of a second, high-index material on the waver. It may be possible fabricate a waveguide using lithography and etching techniques and create alinear resonator beam 20 using high-index material. Subsequently, it may be possible to then clad the waveguide and theresonator beam 20 with a second layer of the low-index dielectric material. A second conventional lithography and etching process may releaseproof mass 22 and the anchor (e.g., base section 64) from a substrate. In some examples, proofmass assembly 14 may include conventional fabrication of a microheater aboveresonator beam 20 to stabilize the accelerometer with respect to temperature. -
FIG. 3 is a conceptual diagram illustrating aresonator beam 100, in accordance with one or more techniques of this disclosure. In some examples,resonator beam 100 is an example ofresonator beam 20 ofFIGS. 1 and2 . As illustrated inFIG. 3 ,resonator beam 100 includes a firstoscillating edge 102 including apeak 104 and a secondoscillating edge 112 including avalley 114.Resonator beam 100 may extend along alongitudinal axis 124 from afirst end 132 to asecond end 134. In some examples,resonator beam 100 may receive one or more optical signals atfirst end 132 from a first circulator (e.g.,first circulator 26 ofFIG. 1 ) andresonator beam 100 may receive one or more optical signals atsecond end 134 from a second circulator (e.g., second circulator 34 ofFIG. 1 ). - In some examples, one or more sinusoidal functions may represent each of first
oscillating edge 102 and second oscillating edge 112 (collectively, "oscillatingedges edges edges - In some examples,
resonator beam 20 may act as a reflective waveguide, allowing optical signals within one or more frequency bands to propagate throughresonator beam 20, and "reflecting" optical signals within one or more other frequency bands. Oscillating edges 102, 112 may define the optical frequency bands whichresonator beam 20 reflects and the frequency bands whichresonator beam 20 allows to pass. For example, the firstoscillating edge 102 may cause theresonator beam 100 to be associated with a first spatial frequency and the secondoscillating edge 112 may cause theresonator beam 100 to be associated with a second spatial frequency, where the first spatial frequency and the second spatial frequency represent a first resonance frequency and a second resonance frequency, respectively. In some examples, the first resonance frequency may represent a resonance frequency ofresonator beam 100 induced by a first light mode (e.g., the TE light mode) and the second resonance frequency may represent a resonance frequency ofresonator beam 100 induced by a second light mode (e.g., the TM light mode). - In some examples, a pi phase shift may exist between the oscillation pattern of first
oscillating edge 102 and the oscillation pattern of secondoscillating edge 112 relative tolongitudinal axis 124. For example, peak 104 of firstoscillating edge 102 may be located at thesame position 126 alonglongitudinal axis 124 asvalley 114 of secondoscillating edge 112. In some cases, each peak of firstoscillating edge 102 may be aligned with a respective valley of secondoscillating edge 112 alonglongitudinal axis 124. Sinceresonator beam 100 includes this pi phase shift,resonator beam 100 may allow a first band of frequencies of a first modulated optical signal to propagate along the length ofresonator beam 100 fromfirst end 132 tosecond end 134 and allow a second band of frequencies of a second modulated optical signal to propagate along the length ofresonator beam 100 fromsecond end 134 tosecond end 132.Resonator beam 20 may reflect frequencies of the first modulated optical signal that are outside of the first frequency band back out offirst end 132 and reflect frequencies of the second modulated optical signal that are outside of the second frequency band back out ofsecond end 134. - The portion of the first modulated optical signal which passes through
resonator beam 20 may indicate the first resonance frequency and the portion of the second modulated optical signal which passes throughresonator beam 20 may indicate the second resonance frequency. As such, the first resonance frequency and the second resonance frequency may be identified based on frequencies that are present in the respective passed modulated optical signals. - In some examples, a compression force or a tension force applied to ends 132, 134 of
resonator beam 100 may affect the first resonance frequency and the second resonance frequency ofresonator beam 100. A proof mass assembly (e.g., proofmass assembly 14 ofFIG. 2 ) may apply these respective compression forces or tension forces responsive to an acceleration of the proof mass assembly. In some cases, a magnitude of a difference between the first resonance frequency and the second resonance frequency caused by the force applied to ends 132, 134 indicates the magnitude of the acceleration of the proof mass assembly. - The
width 122 ofresonator beam 100 may be within a range from 200 nanometers (nm) to 700 nm (e.g., 500 nm), but this is not required. Thewidth 122 ofresonator beam 100 may include any width or range of widths. In some examples, alength 123 ofresonator beam 100 may be within a range from 1 millimeter (mm) to 5mm, but this is not required. Thelength 123 ofresonator beam 100 may include any length or range of lengths. -
Resonator beam 100 is not meant to be limited to the oscillating pattern of firstoscillating edge 102 and the oscillating pattern of secondoscillating edge 112 which are illustrated inFIG. 3 . First oscillatingedge 102 may include more periods than are illustrated inFIG. 3 or less periods than are illustrated inFIG. 3 in some cases. Additionally, or alternatively, secondoscillating edge 112 may include more periods than are illustrated inFIG. 3 or less periods than are illustrated inFIG. 3 in some cases. -
FIG. 4 is a graph illustrating afirst frequency plot 142 and asecond frequency plot 144, in accordance with one or more techniques of this disclosure. As seen inFIG. 4 ,first frequency plot 142 includes afirst peak frequency 146 andsecond frequency plot 144 includes asecond peak frequency 148.First peak frequency 146 andsecond peak frequency 148 are separated by afrequency difference value 150. - In some examples, the
first frequency plot 142 includes one or more frequency components of the modulated firstoptical signal 44 which is delivered to thefirst end 52 ofresonator beam 20.First frequency plot 142 may represent a distribution of frequencies which propagate throughresonator beam 20 fromfirst end 52 tosecond end 54. Sincephotoreceiver 28 receives the passed firstoptical signal 45 which includes frequency components passed byresonator beam 20, thefirst frequency plot 142 may represent one or more frequency components which are present in the passed firstoptical signal 45. In some examples, thefirst peak frequency 146 may represent a first resonance frequency in whichresonator beam 20 mechanically vibrates. - In some examples, the
second frequency plot 144 includes one or more frequency components of the modulated secondoptical signal 48 which is delivered to thesecond end 54 ofresonator beam 20.Second frequency plot 144 may represent a distribution of frequencies which propagate throughresonator beam 20 fromsecond end 54 tofirst end 52. Sincephotoreceiver 28 receives the passed secondoptical signal 49 which includes frequency components passed byresonator beam 20, thesecond frequency plot 144 may represent one or more frequency components which are present in the passed secondoptical signal 49. In some examples, thesecond peak frequency 148 represents a second resonance frequency in whichresonator beam 20 mechanically vibrates. -
Processing circuitry 12 ofFIG. 1 may be configured to determine an acceleration ofaccelerometer system 10 based on thefrequency difference value 150, which represents a difference between thefirst peak frequency 146 and thesecond peak frequency 148. In some examples, a linear or near-linear relationship may exist between a magnitude of the acceleration ofaccelerometer system 10 and a magnitude of the difference between thefirst peak frequency 146 and thesecond peak frequency 148. For example, if the acceleration increases, thefrequency difference value 150 may also increase by a similar proportion and if the acceleration decreases, thefrequency difference value 150 may also decrease. - In some examples, the
first frequency plot 142 may represent one or more frequencies of TE light and thesecond frequency plot 144 may represent one or more frequencies of TM light, but this is not required. In some examples, thefirst frequency plot 142 and thesecond frequency plot 144 may be associated with other types of light. The first resonance frequency may represent a frequency in whichresonator beam 20 vibrates according to a TE resonance frequency mode and the second resonance frequency may represent a frequency in whichresonator beam 20 vibrates according to a TM resonance frequency mode. -
FIG. 5 is a flow diagram illustrating an example operation for determining an acceleration using an opto-mechanical resonator beam, in accordance with one or more techniques of this disclosure.FIG. 5 is described with respect toaccelerometer system 10, proofmass assembly 14,circuit 16, andresonator beam 100 ofFIGS. 1-4 . However, the techniques ofFIG. 5 may be performed by different components ofaccelerometer system 10, proofmass assembly 14,circuit 16, andresonator beam 100 or by additional or alternative devices. - In some examples, processing
circuitry 12 may be configured to determine an acceleration ofaccelerometer system 10. In some examples, theaccelerometer system 10 may include aresonator beam 20 which is configured to mechanically vibrate according to a first resonance frequency and a second resonance frequency. For example,resonator beam 20 may represent an opto-mechanical resonator beam configured to act as an optical waveguide for two or more types of light (e.g., TE light and TM light).Processing circuitry 12 may determine acceleration based on a difference between the first resonance frequency and the second resonance frequency. - First light-emitting
device 24 may emit a first optical signal 44' to first modulator 25 (502). In some examples,first modulator 25 may generate a modulated firstoptical signal 44 to include TE light in order to induce a mechanical vibration inresonator beam 20 according to a TE resonance frequency mode.First modulator 25 may output the modulated firstoptical signal 44 toresonator 20 via first circulator 26 (504). In other words,first circulator 26 directs the modulated firstoptical signal 44 to afirst end 52 ofresonator beam 20 via one or more optical fibers. A portion of the modulated firstoptical signal 44 may travel throughresonator 20 formfirst end 52 tosecond end 54. This portion of the modulated firstoptical signal 44 may include a band of frequencies which corresponds to a resonance frequency ofresonator 20.Photoreceiver 28 may receive passed firstoptical signal 45 from resonator beam 20 (506) via a second circulator 34. In some examples, the passed firstoptical signal 45 may include one or more frequency components of modulated firstoptical signal 44 which are passed byresonator beam 20 which correspond to the resonance frequency. - In some examples, processing
circuitry 12 may generate an error signal. The error signal may reflect any detectable difference between the modulated firstoptical signal 44 and the passed firstoptical signal 45. For example, first light-emittingdevice 24 may emit first optical signal 44' to include frequency components representative of the first resonance frequency ofresonator 20. Any frequency components of the first optical signal 44' may be reflected byresonator beam 20.Photoreceiver 28 may receive the reflected firstoptical signal 46 andprocessing circuitry 12 may generate the error signal based on the reflected firstoptical signal 46.Processing circuitry 12 outputs the error signal to first light-emitting device 24 (508) in order to control first light-emittingdevice 24 to generate first optical signal 44' such that first optical signal 44' does not include frequencies outside of the first resonance frequency. - In response to receiving the passed first
optical signal 45,photoreceiver 28 generates an electrical signal based on the first resonant frequency of resonator beam 20 (510), which is indicated by the passed firstoptical signal 45 received byphotoreceiver 48.Photoreceiver 28 outputs the electrical signal to processingcircuitry 12.Processing circuitry 12 may determine the acceleration ofaccelerometer system 10 based on the electrical signal (512). - In some examples,
accelerometer system 10 includes a second feedback loop which delivers another optical signal tophotoreceiver 28, the other optical signal indicating the second resonance frequency ofresonator beam 20.Processing circuitry 12 may determine the acceleration based on the difference between the first resonance frequency and the second resonance frequency. - In one or more examples, the accelerometers described herein may utilize hardware, software, firmware, or any combination thereof for achieving the functions described. Those functions implemented in software may be stored on or transmitted over, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure.
- Instructions may be executed by one or more processors within the accelerometer or communicatively coupled to the accelerometer. The one or more processors may, for example, include one or more DSPs, general purpose microprocessors, application specific integrated circuits ASICs, FPGAs, or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor," as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules configured for performing the techniques described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements.
- The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses that include integrated circuits (ICs) or sets of ICs (e.g., chip sets). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, various units may be combined or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.
Claims (14)
- An accelerometer system (10) comprising:a resonator;a light-emitting device configured to generate, based on an error signal, an optical signal;a modulator configured to:receive the optical signal;generate a modulated optical signal responsive to receiving the optical signal; andoutput the modulated optical signal to the resonator;a photoreceiver (28) configured to:receive a passed optical signal from the resonator, wherein the passed optical signal represents a portion of the modulated optical signal which passes through the resonator, the passed optical signal indicating a resonance frequency of the resonator;receive a reflected optical signal from the resonator, wherein the reflected optical signal represents a portion of the modulated optical signal which is reflected by the resonator; andgenerate one or more electrical signals based on the passed optical signal and the reflected optical signal; andprocessing circuitry (12) configured to:generate the error signal based on one or more parameters of the reflected optical signal which are indicated by the one or more electrical signals; anddetermine the acceleration based on the resonance frequency which is indicated by the one or more electrical signals.
- The accelerometer system (10) of claim 1, wherein the light-emitting device is a first light-emitting device (24), wherein the error signal is a first error signal, wherein the optical signal is a first optical signal (44'), wherein the modulator is a first modulator (25), wherein the modulated optical signal is a first modulated optical signal, wherein the passed optical signal is a passed first optical signal (45), wherein the reflected optical signal is a reflected first optical signal (46), wherein the resonance frequency is a first resonance frequency, and wherein the accelerometer system (10) further comprises:a second light-emitting device (32) configured to generate, based on a second error signal, a second optical signal (48');a second modulator (33) configured to:receive the second optical signal (48');generate a modulated second optical signal (48) responsive to receiving the second optical signal (48'); andoutput the modulated second optical signal (48) to the resonator,wherein the photoreceiver (28) is further configured to:receive a passed second optical signal (49) from the resonator, wherein the passed second optical signal (49) represents a portion of the modulated second optical signal (48) which passes through the resonator, the passed second optical signal (49) indicating a second resonance frequency of the resonator;receive a reflected second optical signal (50) from the resonator, wherein the reflected second optical signal (50) represents a portion of the modulated second optical signal (48) which is reflected by the resonator; andgenerate the one or more electrical signals based on the passed second optical signal (49) and the reflected second optical signal (50), andwherein the processing circuitry (12) is further configured to:generate the second error signal based on one or more parameters of the reflected second optical signal (50) which are indicated by the one or more electrical signals; anddetermine the acceleration based on the first resonance frequency and the second resonance frequency which are indicated by the one or more electrical signals.
- The accelerometer system (10) of claim 2, wherein the photoreceiver (28) generates the one or more electrical signals to reflect a difference between the first resonance frequency and the second resonance frequency, and wherein the processing circuitry (12) is configured to determine the acceleration based on the difference between the first resonance frequency and the second resonance frequency.
- The accelerometer system (10) of claim 2, wherein the first modulator (25) is configured to emit the modulated first optical signal (44) to a first end (52, 132) of the resonator, and wherein the second modulator (33) is configured to emit the modulated second optical signal (48) to a second end (54, 134) of the resonator.
- The accelerometer system (10) of claim 2, wherein the resonator comprises a mechanical beam extending along a longitudinal axis (124) from a first end (52, 132) to a second end (54, 134), wherein the mechanical beam includes:a first oscillating surface which extends along the longitudinal axis (124) from the first end (52, 132) to the second end (54, 134); anda second oscillating surface opposite the first oscillating surface, wherein the second oscillating surface extends along the longitudinal axis (124) from the first end (52, 132) to the second end (54, 134),wherein the first oscillating surface causes the resonator to vibrate at the first resonance frequency, andwherein the second oscillating surface causes the resonator to vibrate at the second resonance frequency.
- The accelerometer system (10) of claim 5, wherein a first oscillation pattern of the first oscillation surface is offset from a second oscillation pattern of the second oscillating surface along the longitudinal axis (124) such that one or more peaks of the first oscillation pattern align with one or more valleys of the second oscillation pattern.
- The accelerometer system (10) of claim 6, wherein an amplitude of the first oscillation pattern decreases along the longitudinal axis (124) from the first end (52, 132) to a center (56) of the resonator, wherein the amplitude of the first oscillation pattern increases along the longitudinal axis (124) from the center (56) of the resonator to the second end (54, 134), wherein an amplitude of the second oscillation pattern decreases along the longitudinal axis (124) from the first end (52, 132) to the center (56) of the resonator, and wherein the amplitude of the second oscillation pattern increases along the longitudinal axis (124) from the center (56) of the resonator to the second end (54, 134).
- The accelerometer system (10) of claim 1, further comprising a proof mass (22) configured to apply, responsive to the acceleration of the accelerometer system (10) in a first direction (58), a first force to the resonator, causing the resonator to vibrate at the resonance frequency and allowing the processing circuitry (12) to determine the acceleration based on the resonance frequency.
- The accelerometer system (10) of claim 8, wherein the resonance frequency is a first resonance frequency, wherein the acceleration is a first acceleration, and wherein the proof mass (22) is configured to:apply, responsive to a second acceleration of the accelerometer system (10) in a second direction (60), a second force to the resonator, causing the resonator to vibrate at a second resonance frequency and allowing the processing circuitry (12) to determine the second acceleration based on the second resonance frequency,wherein the first direction (58) represents a positive direction along an axis which is normal to a longitudinal axis (124) of the resonator, andwherein the second direction (60) represents a negative direction along the axis which is normal to the longitudinal axis (124) of the resonator.
- The accelerometer system (10) of claim 1, wherein to generate the optical signal based on the error signal, the light-emitting device is configured to generate the optical signal to include a band of frequencies corresponding to the resonance frequency.
- A method comprising:generating, by a light-emitting device based on an error signal, an optical signal;receiving, by a modulator, the optical signal;generating, by the modulator, a modulated optical signal responsive to receiving the optical signal;outputting, by the modulator, the modulated optical signal to a resonator;receiving, by a photoreceiver (28), a passed optical signal from the resonator, wherein the passed optical signal represents a portion of the modulated optical signal which passes through the resonator, the passed optical signal indicating a resonance frequency of the resonator;receiving, by the photoreceiver (28), a reflected optical signal from the resonator, wherein the reflected optical signal represents a portion of the modulated optical signal which is reflected by the resonator;generating, by the photoreceiver (28), one or more electrical signals based on the passed optical signal and the reflected optical signal;generating, by processing circuitry (12), the error signal based on one or more parameters of the reflected optical signal which are indicated by the one or more electrical signals; anddetermining, by the processing circuitry (12), the acceleration based on the resonance frequency which is indicated by the one or more electrical signals.
- The method of claim 11, wherein the light-emitting device is a first light-emitting device (24), wherein the error signal is a first error signal, wherein the optical signal is a first optical signal (44'), wherein the modulator is a first modulator (25), wherein the modulated optical signal is a first modulated optical signal, wherein the passed optical signal is a passed first optical signal (45), wherein the reflected optical signal is a reflected first optical signal (46), wherein the resonance frequency is a first resonance frequency, and wherein the method further comprises:generating, by a second light-emitting device (32) based on a second error signal, a second optical signal (48');receiving, by a second modulator (33), the second optical signal (48');generating, by the second modulator (33), a modulated second optical signal (48) responsive to receiving the second optical signal (48');outputting, by the second modulator (33), the modulated second optical signal (48) to the resonator;receiving, by the photoreceiver (28), a passed second optical signal (49) from the resonator, wherein the passed second optical signal (49) represents a portion of the modulated second optical signal (48) which passes through the resonator, the passed second optical signal (49) indicating a second resonance frequency of the resonator;receiving, by the photoreceiver (28), a reflected second optical signal (50) from the resonator, wherein the reflected second optical signal (50) represents a portion of the modulated second optical signal (48) which is reflected by the resonator;generating, by the photoreceiver (28), the one or more electrical signals based on the passed second optical signal (49) and the reflected second optical signal (50),generating, by the processing circuitry (12), the second error signal based on one or more parameters of the reflected second optical signal (50) which are indicated by the one or more electrical signals; anddetermining, by the processing circuitry (12), the acceleration based on the first resonance frequency and the second resonance frequency which are indicated by the one or more electrical signals.
- The method of claim 12, further comprising:generating the one or more electrical signals to reflect a difference between the first resonance frequency and the second resonance frequency; anddetermining the acceleration based on the difference between the first resonance frequency and the second resonance frequency.
- The method of claim 12, further comprising:emitting, by the first modulator (25), the modulated first optical signal (44) to a first end (52, 132) of the resonator; andemitting, by the second modulator (33), the modulated second optical signal (48) to a second end (54, 134) of the resonator.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US16/996,366 US11630123B2 (en) | 2020-08-18 | 2020-08-18 | Opto-mechanical resonator with two or more frequency modes |
Publications (2)
Publication Number | Publication Date |
---|---|
EP3958001A1 EP3958001A1 (en) | 2022-02-23 |
EP3958001B1 true EP3958001B1 (en) | 2023-01-11 |
Family
ID=77226630
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP21189745.9A Active EP3958001B1 (en) | 2020-08-18 | 2021-08-04 | Opto-mechanical resonator with two or more frequency modes |
Country Status (3)
Country | Link |
---|---|
US (1) | US11630123B2 (en) |
EP (1) | EP3958001B1 (en) |
CN (1) | CN114076831A (en) |
Family Cites Families (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
IT1270954B (en) | 1993-07-21 | 1997-05-26 | Euron Spa | DIESEL COMPOSITION |
US6921894B2 (en) | 2002-09-10 | 2005-07-26 | The Regents Of The University Of California | Fiber optic micro accelerometer |
TWI233097B (en) | 2003-09-04 | 2005-05-21 | Lite On It Corp | Device capable of detecting vibration/shock |
US7355723B2 (en) | 2006-03-02 | 2008-04-08 | Symphony Acoustics, Inc. | Apparatus comprising a high-signal-to-noise displacement sensor and method therefore |
US8334984B2 (en) | 2008-08-22 | 2012-12-18 | The Regents Of The University Of California | Single wafer fabrication process for wavelength dependent reflectance for linear optical serialization of accelerometers |
JP5341807B2 (en) * | 2010-03-26 | 2013-11-13 | 株式会社東芝 | Acceleration sensor |
US8879067B2 (en) | 2010-09-01 | 2014-11-04 | Lake Shore Cryotronics, Inc. | Wavelength dependent optical force sensing |
WO2013052953A1 (en) | 2011-10-08 | 2013-04-11 | Cornell University | Optomechanical sensors based on coupling between two optical cavities |
US9618531B2 (en) | 2012-03-02 | 2017-04-11 | California Institute Of Technology | Optomechanical accelerometer |
US9001336B1 (en) * | 2013-10-07 | 2015-04-07 | Honeywell International Inc. | Methods and apparatus of tracking/locking resonator free spectral range and its application in resonator fiber optic gyroscope |
US9239340B2 (en) * | 2013-12-13 | 2016-01-19 | Intel Corporation | Optomechanical sensor for accelerometry and gyroscopy |
US9285391B2 (en) | 2013-12-13 | 2016-03-15 | Intel Corporation | Optomechanical inertial sensor |
US9874581B2 (en) | 2015-05-15 | 2018-01-23 | Honeywell International Inc. | In-situ bias correction for MEMS accelerometers |
WO2017030620A1 (en) | 2015-05-29 | 2017-02-23 | Massachusetts Institute Of Technology | Apparatus and methods for photonic integrated resonant accelerometers |
US9983225B2 (en) * | 2015-06-29 | 2018-05-29 | Honeywell International Inc. | Optical-mechanical vibrating beam accelerometer |
FR3050820B1 (en) | 2016-04-29 | 2018-04-13 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | MEASUREMENT SYSTEM RESULTING IN IMPROVED RESOLUTION |
US10571483B2 (en) | 2016-11-09 | 2020-02-25 | Massachusetts Institute Of Technology | Integrated resonant accelerometer using optical strain sensor |
US10488429B2 (en) | 2017-02-28 | 2019-11-26 | General Electric Company | Resonant opto-mechanical accelerometer for use in navigation grade environments |
GB201809137D0 (en) | 2018-06-04 | 2018-07-18 | Bangor Univ | Improvements in and relating to waveguides |
US10705112B1 (en) | 2019-04-22 | 2020-07-07 | Honeywell International Inc. | Noise rejection for optomechanical devices |
-
2020
- 2020-08-18 US US16/996,366 patent/US11630123B2/en active Active
-
2021
- 2021-07-22 CN CN202110832896.XA patent/CN114076831A/en active Pending
- 2021-08-04 EP EP21189745.9A patent/EP3958001B1/en active Active
Also Published As
Publication number | Publication date |
---|---|
US11630123B2 (en) | 2023-04-18 |
CN114076831A (en) | 2022-02-22 |
US20220057427A1 (en) | 2022-02-24 |
EP3958001A1 (en) | 2022-02-23 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US11815630B2 (en) | Integrated optics quantum weak measurement amplification sensor for remote sensing | |
JP2007286062A (en) | Optical resonator gyro with external resonator beam generator | |
Liu et al. | All-fiber laser-self-mixing sensor for acoustic emission measurement | |
Sanders et al. | Development of compact resonator fiber optic gyroscopes | |
EP3958001B1 (en) | Opto-mechanical resonator with two or more frequency modes | |
Sanders et al. | Improvements of compact resonator fiber optic gyroscopes | |
CN112240940B (en) | Opto-mechanical structure with corrugated edges | |
CN111796117B (en) | Accelerometer for determining acceleration based on modulated light signal | |
CN111830282B (en) | Feedback cooling and detection for optomechanical devices | |
US11119114B2 (en) | Anchor structure for securing optomechanical structure | |
US11079227B2 (en) | Accelerometer system enclosing gas | |
Ying et al. | How Laser Diode (LD) Intensity Modulation Induced by Current Tuning Affects the Performance of an Open-loop Resonator Fibre Optic Gyro (R-FOG) with Sinusoidal Wave Modulation. | |
US11372019B2 (en) | Optomechanical resonator stabilization for optomechanical devices | |
JPH06501547A (en) | speedometer | |
JPS6355035B2 (en) | ||
Song et al. | Analysis of vibration error in fiber optic gyroscope | |
US5652390A (en) | Method and device for autonomous measurement of an irregular movement based on resonatory sensor | |
US20230184554A1 (en) | Control of laser frequency in an optical gyroscope with a ring resonator | |
EP4040110A1 (en) | Optical gyroscope with a resonator having bias error reduction | |
JP2024021912A (en) | laser interferometer | |
JP2548044B2 (en) | Optical interference gyro | |
Mao et al. | A high-resolution displacement sensor based on multiple feedback effect of birefringence dual frequency lasers | |
Zhang et al. | Research of Mach-Zehnder interferometer in electro-optic integrated accelerometer | |
Yanjun et al. | Research of Mach-Zehnder Interferometer in Electro-optic Integrated Accelerometer | |
JPH0510771A (en) | Light phase modulator and optical rotation detecting device using it |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION HAS BEEN PUBLISHED |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE |
|
17P | Request for examination filed |
Effective date: 20220318 |
|
RBV | Designated contracting states (corrected) |
Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: GRANT OF PATENT IS INTENDED |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: G01H 13/00 20060101ALN20220831BHEP Ipc: G01H 9/00 20060101ALN20220831BHEP Ipc: G01P 15/097 20060101ALI20220831BHEP Ipc: G01P 15/093 20060101AFI20220831BHEP |
|
INTG | Intention to grant announced |
Effective date: 20220914 |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE PATENT HAS BEEN GRANTED |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: FG4D |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: EP |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R096 Ref document number: 602021001205 Country of ref document: DE |
|
REG | Reference to a national code |
Ref country code: IE Ref legal event code: FG4D |
|
REG | Reference to a national code |
Ref country code: AT Ref legal event code: REF Ref document number: 1543726 Country of ref document: AT Kind code of ref document: T Effective date: 20230215 |
|
REG | Reference to a national code |
Ref country code: LT Ref legal event code: MG9D |
|
REG | Reference to a national code |
Ref country code: NL Ref legal event code: MP Effective date: 20230111 |
|
REG | Reference to a national code |
Ref country code: AT Ref legal event code: MK05 Ref document number: 1543726 Country of ref document: AT Kind code of ref document: T Effective date: 20230111 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: NL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 |
|
P01 | Opt-out of the competence of the unified patent court (upc) registered |
Effective date: 20230525 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: RS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: PT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230511 Ref country code: NO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230411 Ref country code: LV Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: LT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: HR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: ES Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: AT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: PL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: IS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230511 Ref country code: GR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230412 Ref country code: FI Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R097 Ref document number: 602021001205 Country of ref document: DE |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SM Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: RO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: EE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: DK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 Ref country code: CZ Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20230824 Year of fee payment: 3 |
|
26N | No opposition filed |
Effective date: 20231012 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SI Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R119 Ref document number: 602021001205 Country of ref document: DE |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: MC Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: MC Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LU Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20230804 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LU Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20230804 |
|
REG | Reference to a national code |
Ref country code: BE Ref legal event code: MM Effective date: 20230831 |
|
REG | Reference to a national code |
Ref country code: IE Ref legal event code: MM4A |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20230111 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20230804 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20230804 Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20240301 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: BE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20230831 |